Polymeric Stent Post-Electron Beam Conditioning
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Solution Overview
Problem
Medical stents made from polymers face challenges in maintaining consistent mechanical properties and bioresorption kinetics due to changes during processing and storage, leading to variations in strength and durability, which complicates their use in vascular treatments and drug delivery.
Innovation Solution
A method involving controlled temperature exposure of polymeric stents, specifically between 30°C to 55°C, for durations ranging from 8 hours to several days, to stabilize the polymer scaffolding and reduce undesirable changes in properties, ensuring consistent radial strength and bioresorption profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymeric stents undergo processing and storage, then the stents can be manufactured and delivered for use, but the mechanical properties and bioresorption kinetics of the polymer change, leading to variations in strength and durability
Solution Approach 1:
The patent applies preliminary action by performing electron beam conditioning on the polymeric stent before final sterilization and delivery. This pre-conditioning step stabilizes the polymer's mechanical properties and bioresorption kinetics, preventing undesirable changes that would otherwise occur during subsequent processing, storage, and shelf-life. The conditioning is done at a stage when the stent is already manufactured but before it undergoes final sterilization, allowing the polymer structure to be optimized in advance.
Solution Approach 2:
The patent utilizes parameter changes by exposing the polymeric stent to controlled electron beam radiation with specific energy levels (e.g., 10-50 kGy) and dosages to induce cross-linking or other stabilizing effects. By carefully controlling the electron beam parameters (energy, dosage, exposure time), the polymer's mechanical strength, toughness, and bioresorption rate are stabilized without compromising the stent's structural integrity or biocompatibility.
2Reliability
If additional processing operations are performed on polymeric stents, then the stents can be sterilized and packaged for delivery, but the properties of the polymer continue to change, affecting strength and toughness
Solution Approach 1:
The electron beam conditioning is performed as a preliminary action before final sterilization and packaging. This sequence ensures that the polymer's mechanical properties are stabilized before the stent undergoes subsequent processing steps that might otherwise cause degradation. The conditioning creates a more resilient polymer structure that can withstand the stresses of sterilization and packaging without significant loss of strength or toughness.
Solution Approach 2:
The patent converts the potentially harmful effect of electron beam radiation (which could degrade the polymer) into a beneficial effect by using controlled exposure to stabilize and enhance the polymer's mechanical properties. The electron beam, when applied at appropriate energy levels and dosages, induces cross-linking that improves strength and toughness rather than degrading the material. This transforms what could be a harmful processing step into a beneficial conditioning treatment.
3Duration of action of stationary object
If polymeric stents are stored for extended periods, then they remain available for clinical use, but the properties of the polymer change over time, reducing reliability
Solution Approach 1:
The electron beam conditioning is performed in advance, before the stent enters long-term storage. This preliminary stabilization creates a more robust polymer structure that is resistant to time-dependent degradation. The conditioning establishes a stable molecular structure that maintains consistent mechanical properties and bioresorption kinetics throughout the stent's shelf-life, enabling reliable long-term storage without property drift.
Solution Approach 2:
The electron beam conditioning acts as a protective measure that cushions the polymer against future degradation during storage. By pre-treating the polymer with controlled electron beam exposure, the patent creates a more stable and resilient material structure that is better equipped to withstand the effects of time, temperature fluctuations, and environmental factors during extended storage periods, thereby maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach stabilizes the polymer properties, reducing variations in radial strength and molecular weight, thereby enhancing the reliability and effectiveness of polymeric stents for vascular applications and drug delivery systems.
Implementation Method 1
exposing a polymeric stent with a polymeric scaffolding to a temperature equal to, approximately equal to, or greater than 30° C. and not more than about 15° C. less than the glass transition temperature of the polymeric scaffolding
Implementation Method 2
The polymeric scaffolding may be formed from a polymeric article that has been deformed by the application of stress at a temperature greater than that of the glass transition temperature of the polymeric article
Implementation Method 3
the properties of a polymer can change both during processing and after processing. These properties include mechanical properties such as strength and toughness as well as bioresorption kinetics
Data Source
AI summary
Methods are disclosed for conditioning a polymeric stent after sterilization, and/or after crimping and before packaging, such that the properties of the polymeric stent fall within a narrower range of values. The stent is exposed to a controlled temperature at or above ambient for a period of time after radiation sterilization and/or after crimping and before sterilization. As a result, the polymeric stent properties, particularly radial strength and number-average molecular weight of the polymer of the polymeric stent, fall within a narrower range.